Electrically-heated cooker.



A. J, KERCHER. BLBGTRIGALL-Y HEATED cooKBR.

APPLICATION FILED NOV. 13, 1911.

Patented Dec. 1'?, 1912-.

2 SHEETS-SHEET 2.

Zanini/1f 1-1 1S ATTUHNEYS ABTHUBJ'. KERCHEB, OF BERKELEY, CALIFORNIA,ASSIGNOR T0 BERKELEY ELECTRIGl GOOKEB COMPANY, OF BERKELEY, CALIFORNIA,A,GORPOBATION 0F CALIFORNIA.

ELECTRICALLY-HEATED COOKER.

Specification of Letters Patent.

Application led November 13, 1911. Serial No. 659,894.

. Patented Dec. 17, 1912.

To all whom it may concern:

Be it known that I, ARTHUR J. KERCHEn, a citizen of the United States,anda resident of Berkeley, county of Alameda, and State of California,have invented certain new and useful Improvements in Electrically-HeatedCookers, of which the following is a specification.

The invention relates to cookers which are adapted to be heated to theproper temperature by means of an electric current and more particularlyto a device in which the electric circuit is automatically opened andclosed to maintain the temperature substantially constant.

The object of the invention is to pro'- vide an electrically heatedcookerin which the electric current is automatically controlled tomaintain a substantially constant temperature within the cooker.

Another object of t-he invention is to provide an electrically heatedcooker in which the electric current is controlled by variations inpressure Within the lcooker `caused by variations in temperature.

A further object of the invention is to provide an electrically heatedcooker provided with a quick throw switch in the elec- A further objectof the invention isto provide an electrically heated cooker in whichnofthermal connection is established between the heating unitsand theoutside air, so that all of the heat generated is utilized in cooking.

The device possesses other advantageous features, which, with theforegoing will be set forth at length in the following description,where I shall out-line in full that form or embodiment of the inventionwhich I have selected for illustration in the drawings, accompanying andYforming part of the present specication.- The novelty of the inventionwill be included in the claim succeeding said description. From thisitwill be apparent that I do not restrict myself to the showing made bysuch drawings and descriptions as I may adopt many variations within thescope `of my invention as'- eXpressed in said claims.

Referring to the drawings Figure 1 is a vertical section of the cookerof my invention completely inclosed in an envelop of heat -insulatingmaterial. Fig. 2 is a vertical section through the lower part of thecooker and the quick throw switch. Fig. 3 is a plan lview of the underside of t-he cooker showing the switch and the heating units.

The heating element is adapted to heat abody of liquid in a closedreceptacle from which the heat is transferred to the substance to becooked and the regulating and .Controlling means is.arrangedvto beoperated by the change in pressure within the receptacle, caused by achange in temperature. At a given vtemperature a certain pressure isVobtained and the controlling mechanism is arranged to open the circuitwhen such temperature is exceeded and to close the circuit when thetemperature drops below this point. By this means the substance to becooked is subjected to a substantially constant even temperature and iscooked to better advantage than in instances where the temperaturevaries in any subst-antial degree.

By inclosing the cooker in an envelop of heat insulating material, allof the heat generated by the electric current is available to cook thematerial and a very etticient cooker is obtaned, but it is evident thatthe cooker could be used without t-he heat insulating material andperform its functions although in a less efficient manner.

The current controlling apparatus comprises a quick-throw switch whichis operated by changes in the pressure tovopen and close the electriccircuit. This type of switch is advantageous in that itimmediatelybreaks the circuit when the critical pressure is reached andseparates the contacts abruptly, so that no sparkingor arcing occurs.The advantage of the quick separation or contacting of the lterminals isapparent to those familiar with the use of electric currents'and needsno further eX- planation.

The cooker consists of a receptacle 2 having double side walls 3-4 anddouble bottom walls 5 6l spaced apart to form a chamber 7 therebetween.The side wall 3 and the bottom wall 5 are formed integral and the sideWall 4 and the bottom wall 6 arepformed integral, and the side walls 3and 4 are secured together at their upper ends. This joint is formedbyalloying or fusing the metal of the two walls together therebyreceptacle.

tight chamber 7. The side wallsk may be formed perpendicular, as shown,or may be inclined, depending upon the shape of the cooking vessel 8,which-is to be placed in the cooker.

A quantity of Vwater or other liquid is placed in the chamber 7 so thatit completely covers the bottom thereof and the chamber is exhausted sothata vacuum exists therein. Thisv is preferably 'accomplished byproviding a small vent to the chamber and heat-- ing the water thereinto the boiling point, so that the air therein is expelled and only steamand water remain in the chamber. The vent is then sealed and as thereceptacle cools a vacuum is formed in the chamber. Therefore, as thereceptacle is subsequently heated, the pressure therein equals that offorming an air the atmosphere whenthe temperature oit the water andsteam reaches 212 Fahrenheit. A 'further rise in temperature above thispoint increases the pressure within the chamber and the elect-riccircuit is automatically opened. A `V The heating units 12 of anysuitable construction are arranged on thebottom 6 of the receptacle' 2and. are spaced apart therefrom by a strip of thin insulation 13, suchas mica.. These units 12 are held in place by the short channel bars 14,from which they are also insulated.` The channels-14 are held in placeby bolts 15 passing through the bottom wall 6 and engaging angles 16within the chamber. The joints bet-Ween the bolts and the bottom wall 6are preferably alloyed to prevent any leakage. This construction acts tostiften the bottom wall 6 and prevent it from collapsing as cools and avacuum is formed therein. In the interior electric circuit whichterminates at the plug 17,

thro-w electric switch which is -operatedby variations in pressurewithin the chamber to open and close the circuit. The switch comprisesan upper or stationary arm carrying contact 18 and a lower movable arm19 carrying contact 21. The arm 19 is pivoted in a bracket 22 which isattached to the casing 23, the outer or contact end of the arm beingpressedv upward normally by the spring-24 attached to an ear on the armand \to a bracket 25 attached to the bottom of the This bracket 25 isattached to the vbottom 6 by an alloy whichv melts at a temperatureabove 212 Fahrenheit, so that, should the switch fail to operate to openthe circuit at theproper temperature, a .further rise in, temperaturewill melt the alloy, release the sp1- ing 24 and allow the arm 19 to droand therebyopen the circuit.

Wit in the chamber 7, and secured in the casing `23 is 'a spring'diaphragm of the buc` kling type 26, which is sprung into its oppositepositions by variations in pressure within the chamber. The connectionbethe receptacle I have placed a quick tween the spring diaphragm an-dthe supporting casing is alloyed to prevent leakage. The casing issupported in the chamber by the screws 27 passing through depressedportions 28 in the bottom wall 5./ These depressions serve to space the-diaphragm away fromthe` bottom 5, and also allow the bottom to be flushon the inside. After the screws are seated, an alloy is placed in thedepressions .to insure a. hermetic seal. Arranged in the casing 23 withits ends in close relation with the diaphragm and the arm 19 is amovable pin 31 which transfers the motion of the diaphragm to the switcharm. Ordinarily the diaphragm is fiexed upward andthe switch is closed,but when the pressure within the chamber reaches a certain criticalpoint, the diaphrag springs or buckles to itsreverse position, `abruptlyseparating the contacts and opening the circuit. y Similarly, as thepressure subsequently decreases, the diaphragm springs back and allowsthe switch to close quickly. For the purpose ofret'aining the heattherein, the cooker is inclosed in an envelop of heat insulatingmaterial 32completely surrounding it on the sides and bottom and aremovable cover 33 isprovided to close the top. I have also consideredit advisable to surround the heating units and the switch with sheets 34of asbest-os or other fire proof material.

The cooker is supported in the heat insulating container by ring 35bearing against the top of the receptacle 2. In order to prevent theloss of heat through the ring 35 I interpose a ring 37 of packing orother poor heat conducting material between the receptacle 2 and thering 35, so that the thermal connection is broken and the heat may notbelost byconduction.

I claim:

1. An electrically heated cooker compris'- ing a vacuumized receptaclepartly filled with liquid and a heating element 1n close relation tosaid receptacle.

2. An electrically heated cooker comprising a vacuumized receptaclepartly filled with liquid, a heating element in close relation to'saidreceptacle, an electric c'ircuit 'for the heating element and a quickthrow switch in said circuit said switch being arranged. adjacent saidreceptacle.

y3. An electrically heated cooker comprising a vacuumized receptacle.partly filled with liquid, a heating element in close relation to saidreceptacle, a spring diathe annular metallic n phragm of the bucklingtype within said re- Y ceptacle, an electric circuit for the heatingelement, and a switch in said circuit ar-' ranged to be operated by saiddiaphragm.

4. An electrically heated cooker 'compris' ing a vacuumized receptaclepartly filled with liquid, a heating element in close relation to saidrecept-acle,an electric circuit for the heating element and a quickthrow switch in said circuit adapted to be operat ed by variations inpressure within said receptacle.

5. An electrically heated cooker comprising a vacuumized receptacle'partly filled with liquid, a heating element arranged externally of thereceptacle upon the wall thereof, a spring diaphragm of the bucklingtype within lsaid receptacle adapted to be sprung by variations Ainpressure therein, an electric circuit forv the heating element, a quickthrow switch in said circuit and means connecting said switch and saiddiaphragm.

6. In an electrically heated cooker, a heating element, an electriccircuit for the heating element, a switch in said` circuit, a springadapted to hold said switch in the closed position and means forreleasing said spring and allowing the switch to open,

when the temperature exceeds a certain4 maximum.

7. In an electrically heated cooker, a receptacle having aclosed chambertherein, a heating element in close relation thereto, an electriccircuit for the heating element, a switch in said circuit, a bucklingdiaphragin in said receptacle adapted to be operated by variat-ions inpressure therein, means connecting said diaphragm with the movable armof the switch, means tending to hold said arm in the closed position andmeans operating to release said holding means when the temperature inthe receptacle reaches a certain maximum.

8. The combination of a casin ofl heat insulating material, a coverthere or; a vacuumized receptacle within said casing, a heatingelement'in close relation to said receptacle an electirc circuit for theheating element and a quick throw switch in said circuit adapted to beoperated by variations in pressure within the receptacle.

9. An electrically heated cooker comprising a vacuumized receptaclehaving a depression therein adapted to receive the material to becooked, said receptacle being partly filled with water', heatingelements attached to the bottom thereof, an electric circuit for theheating element and a switch in said circuit adapted to be operated byvariations in pressure 4within the receptacle. y

10. A11 electrically heated cooker comprising Va hermetically sealedvacuumized receptacle partly filled with liquid, heating elementsarranged adjacent and external vthereto at the bottom, an electriccircuit for the heating element, a quick throw switch in said circuitprovided with means for holding it normally in the closed position, aspring diaphragm of the buckling type arranged within the receptacleadapted to be sprung by variations. in pressure within the receptacleand a pin coacting with said diaphragm and switch, adapted to open saidswitch abruptly as the diaphragm springs downward.

In testimony whereof, I have hereunto set Imy hand at San Francisco,Cal., this 6th day of November, 1911.

ARTHUR J. KERCHER.

In presence of- H. G. PRosT, R. HEFFERMAN.

